Method for manufacturing integral elastic supports, and supports obtained with this method

ABSTRACT

A method for manufacturing integral elastic supports formed by an upper covering (2), by an intermediate filler (3) and by a semirigid shell (4) entails the use of a mold with a hollow lower part, a flat upper part, and at least one intermediate plate. The method includes the following steps: opening of the mold; deposition on the lower part of a covering sheet with an excess border; securing of the excess border by means of the locking plate; deformation of the covering sheet in vacuum; pouring of a first layer of a gel compound in the fluid state; coupling of a semirigid shell to the upper part of the mold; pouring of a second layer of an expandable resin in the fluid state; closing of the mold; opening of the mold and removal of the finished support. The expandable resin is poured onto the gel compound after a period of time that is sufficient to allow the compound to assume a consistency and shape of its own but is shorter than the full polymerization time so as to allow it to react at least partially with the resin.

This is a Division of application Ser. No. 08/168,211 filed Dec. 17,1993, now U.S. Pat. No. 5,441,676.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for manufacturing integralelastic supports and to an integral support obtained by means of thismethod.

Typical examples of elastic supports manufactured according to thepresent invention are the backs and seats for contoured chairs orwheelchairs, for the physically challenged and older people, supportsfor parts of the bodies of patients forced to long periods ofimmobility, seats for industrial vehicles, and saddles for bicycles andmotorcycles.

2. Description of the Prior Art

It is known that the region of contact between the surface of thesupport and the part of the human body that must be supported isnormally concentrated proximate to the ischial bones of the pelvis.Accordingly, specific pressure is relatively high in these regions andcan prevent oxygenation of tissues and correct blood circulation,causing so-called bedsores and other similar disorders. In other cases,as in bicycle saddles used by healthy individuals and athletes, the highspecific pressure can create extremely troublesome irritations oraffections of the tissues and can, in some cases, temporarily orpermanently damage delicate organs, such as the genitalia and theprostate. On this subject, reference is made to the article published by"Bicycling" magazine of July 1993, pages 57-60. These effects aresometimes increased by the presence of discontinuities or folds on thecovering of the support, caused by lack of tension or of adhesion of thecovering to the underlying filler.

In order to reduce the specific pressure in the above mentioned delicateregions of the body, supports have been produced that are formed by anouter covering that encloses a padding which includes one or more layersor sacs of materials that are more resilient than the rest of thesupport. The materials used for this purpose are gaseous, such ascompressed gas or air, particularly flexible elastomeric materials,open-cell polylurethane foams, some high-viscosity oily or thixotropicliquids, or combinations of these materials. Examples of these supportsare given by French patent No. 2,306,866, by German patent No. 75,799,by European patent No. 0 013 527 and by U.S. Pat. Nos. 718,850,3,161,436, 4,012,072, 3,807,793, 4,588,229, and 4,808,469.

Supporting structures with elastomeric materials in gel form that behavelike liquids but have partial resilience or elastic memory have recentlybeen perfected; reference is made to U.S. Pat. Nos. 3,548,420 and3,663,973 on this subject.

These known supporting structures generally include a layer of gelmaterial formed by a composition of siloxane or organosiloxane polymers,as disclosed by U.S. Pat. No. 3,020,260. In all these knownapplications, the gel material bas no shape of its own and musttherefore be enclosed within impermeable walls or appropriate containersmade of flexible material. After being enclosed, the gel can beintegrated in a filler made of foamed elastomeric material.

The bicycle saddle structure produced in accordance with U.S. Pat. No.4,815,361 in the name of Chiarella has a supporting frame made of nylon,polypropylene or other relatively rigid plastic material; a layer offoamed elastomeric material, for example polyurethane foam, obtainedseparately by molding in a closed mold so that it has a recess thatcorresponds to the ischial region in its central part, is glued onto theframe. The recess is meant to accommodate a sac of organosiloxane gelmaterial, also as disclosed by U.S. Pat. No. 3,020,260. These threeparts are mutually superimposed, and a covering of flexible material,for example Lycra or fabric, is applied on them, stretched and anchoredto the lower edges of the frame. This saddle and the associatedmanufacturing method have numerous disadvantages, mainly linked to theuse of the particular organosiloxane gel. Since this material does nothave a shape of its own, it must in fact be contained laterally by thelateral edges of the cavity formed on the upper part of the polyurethanefoam filler. The filler must therefore be shaped separately and allowedto cure completely in order to contain the gel insert downward andlaterally. Furthermore, since the silicone gel is unstable, i.e. has alimited shelf life and breaks down easily if it is subjected to repeatedand rather intense stresses, releasing highly impregnating polyhydricalcohols, it must be carefully isolated within a sealed sac made ofimpermeable material of a certain thickness, for example polyethylene,to avoid leaks or impregnation of the covering. Consequently, thecovering cannot be placed directly in contact with the gel compound butmust be protected by an intermediate layer that unavoidably reduces theelastic fluid-mechanical properties of the compound. Generally, thesaddle manufacturing method according to U.S. Pat. No. 4,815,361requires an excessive use of labor, with considerable finished-productcosts. The method for stretching the support covering layer also doesnot ensure a uniform supporting surface that is free from creases ordiscontinuities that reduce the final quality of the finished supportand are poorly accepted by users.

The aim of the present invention is to provide an integral elasticsupport that includes an insert made of gel material that can beobtained by means of all extremely simple and repetitive method, with avery limited use of labor, and can thus be automated substantiallycompletely, so as to considerably reduce production costs and times.

An object is to provide an integral elastic support that includes a gelinsert or layer that maximally exploits the hydroelasticity propertiesof this material.

Another object is to provide a discontinuous process for themass-production of integral gel supports that are substantially freefrom discontinuities and surface creases and have a high quality level.

SUMMARY OF THE INVENTION

This aim and these objects are achieved by the method according to theinvention, which entails the use of at least one mold that includes alower part, provided with a cavity that is open upward and reproducesthe resting surface of the support, a substantially flat upper part thatreproduces the bottom of the support, and at least one intermediateplate for retaining the covering, this method comprising the followingsteps: opening the mold so as expose the cavity of the lower part of themold: depositing on the lower part a substantially airtight coveringsheet the border of which exceeds the contour of the cavity; securingthe excess border against the lower part by superimposing the retentionplate on it; permanent forming of the covering sheet by producing vacuumon the internal wall of the cavity; pouring of a first layer of a gelcompound in the fluid state onto the bottom of the deformed sheet;detachable coupling of a shell made of semirigid plastic to the upperpart of the mold; pouring of a second layer of an expandable resin inthe fluid state onto the first gel layer; closing of the mold bysuperimposing and locking the upper part of the mold on the plate and onthe lower part of the mold; keeping the mold in closed condition toallow the foaming and complete polymerization of the resin and of thegel compound; opening of the mold and removal of the finished support;wherein the expandable resin is poured onto the gel compound after aperiod of time that is sufficient to allow the compound to assume acertain consistency and shape of its own but is shorter than the fullpolymerization time of the compound, so as to allow it to react at leastpartially with the expandable resin.

The gel compound and the expandable resin have such compositions as toform, prior to their complete polymerization, chemical bonds at theirseparation surface.

The separation surface between the gel compound and the expandable resinis constituted by the meniscus of gel compound poured onto the bottom ofthe deformed covering sheet.

The gel compound consists of a mixture of approximately 20% by weight ofa polyurethane matrix having a high relative molecular mass,approximately 80% by weight of a liquid dispersant that includes one ormore polyhydric alcohols with hydroxyl groups inhigher-than-stoichiometric proportions, with the addition of a catalystand of possible additives and in the absence of plasticizers. Inparticular, the gel compound has a composition in accordance with U.S.Pat. No. 4,404,269.

By means of a process according to the invention and by using the abovementioned materials, one obtains an elastic support that is formed by anouter covering made of flexible material superimposed on apolyurethane-foam filler layer which is in turn anchored to asubstantially rigid supporting shell, wherein the covering and thefiller layer are chemically bonded to each other and to the underlyingshell so as to form an integral support. At least one layer or an insertof polyurethane gel compound, chemically bonded to the upper and lowerlayers by means of an addition polymerization reaction, is interposedbetween the covering and the filler layer.

By virtue of the chemical bonds between the various layers and theunderlying shell, and by virtue of the chemical properties of thepolymerized compound, it is not necessary to laterally contain the layerof gel, which instead remains coupled to the foamed resin layer at themeniscus of gel compound deposited in the cavity of the mold.

It is thus possible to give the gel layer the most appropriate shapes byforming depressions of the desired shape on the bottom of the lower partof the mold. The gel compound insert thus forms one or more protrusionswith respect to the upper surface of the filler which locally reducespressure on the body of the user with respect to the surroundingregions, where the polyurethane-foam filler layer is more rigid.

Furthermore, since the gel compound is highly stable, the layer of gelcan be placed directly in contact with the outer covering, and itselastic and plastic properties are not impaired by containment bodies asin previous supports.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described hereinafter by way of non-limitative exampleby means of a method and a support according to the invention, withreference to the accompanying drawings, wherein:

FIG. 1 is a perspective view of a support according to the invention,particularly a bicycle saddle;

FIG. 2 is a sectional view of the support of FIG. 1, taken along thevertical longitudinal plane II--II;

FIG. 3 is a schematic sectional view, taken along a vertical plane, of amold for performing the method according to the invention, during use;

FIG. 4 is an enlarged-scale view of a detail of FIG. 3; FIG. 5 is asectional view of the mold of FIG. 3, taken along the plane V--V;

FIGS. 6 to 15 schematically illustrate the various steps of themanufacturing method according to the invention for producing thesupport of FIG. 1;

FIG. 16 is a schematic top view of an apparatus for manufacturingaccording to the invention shown in FIGS. 6 to 15.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

FIGS. 1 and 2 illustrate an example of an integral support according tothe invention, constituted by a bicycle saddle which is particularlycomfortable even for prolonged use and is such as to reduce pressure inthe pelvic region and in the urogenital system.

The saddle 1 includes an upper covering 2 that covers a multilayerelastic filler, generally designated by the reference numeral 3, and ashell 4 made of semirigid plastic material. In particular, the shell isshaped so as to form a stiffened region and a bracket for anchoring to abicycle frame 5 which is schematically shown in broken lines.

Preferably, the covering can be formed by a multilayer flexible laminarmaterial which includes for example a film of polyurethane materialsuperimposed on a compact base layer of PVC or of PVC-impregnated fabric(Lycra) and on a layer of foamed PVC. The lower surface of the coveringis coated with a polyurethane-based primer that contains hydroxyl groupscapable of chemically bonding to the filler of the support. Themultilayer covering 2 has compactness characteristics combined with acertain softness to the touch and with airtightness to allow itsvacuum-forming.

The filler 3 includes a lower layer 6 constituted by a foamed polymericresin. An upper layer or insert 7, made of a gel compound, issuperimposed on the lower layer and chemically bonded to it by additionpolymerization reactions. The plan dimensions of the insert are smallerthan those of the complete support, and when not in use it protrudesupward with respect to the surface of the lower layer 6. The shape ofthe insert is such as to form a pad of material that yieldshydroelastically at the most delicate parts of the user, namely thepelvic bones and the urogenital system. By virtue of the chemical bondbetween the two layers 6 and 7 of the filler, the gel compound isself-supporting and does not have to be contained laterally in a presetposition. Consequently, the layer 7 can be placed directly in contactwith the covering 2, which is in turn chemically bonded both to the gelcompound and to the foamed resin.

Advantageously, the gel compound is a polyurethane-based mix inaccordance with U.S. Pat. Nos. 4,404,296 and 4,456,642 in the name ofthe German company Bayer AG, manufactured and marketed by the samecompany under the trade-name LEVAGEL. In particular, the mix is formedby two main components A and B, where A is constituted by approximately20% by weight (with respect to the weight of A+B) of a polyurethanematrix having a high relative molecular mass, cross-linked with covalentbonds, and B is approximately 80% by weight (with respect to the weightof A+B) of a liquid dispersant that is closely bonded to thepolyurethane matrix by secondary valence forces, with the addition of acatalyst to increase the addition polymerization reactions between theisocyanates and the hydroxyl groups of the two main components and ofany additives, such as fibers and dyes. Further details regarding thechemical formula and the process for obtaining this gel compound areincluded in the above mentioned U.S. patents, the contents of which areincluded as reference in the present invention. It is interesting tonote that the hydroxyl groups contained in component B are present inhigh stoichiometric excess with respect to the isocyanate groups ofcompound A, so as to form a urethane polymer dissolved in the polyhydricalcohol excess which gives the compound a gelatinous but firmappearance. After full polymerization, by virtue of the secondaryvalence forces between the polyhydric alcohols and the urethane matrixthe compound maintains a surprising stability even after prolonged use,with repeated impacts and fatigue stresses. The gel also has a lowcomponent migration, so that the polyhydric alcohols dissolved in it donot separate from the urethane matrix, and it therefore does not need tobe contained in an impermeable capsule or container as in the case ofthe silicone gels of the prior art. The gel insert 7 can thus be placeddirectly in contact with the covering 2 and can fully develop itselastic fluid-mechanics properties.

The lower layer 6 of the filler 3 can be formed by means of a foamedresin produced by addition polymerization reactions of diols and trioIswith a relative molecular mass of 4500 to 6000 and methylenediisocyanate-based isocyanates (MDI). The polyurethane foam obtainedfrom the reaction between the isocyanate and the water present in themix has a density approximately 150-250 kg/m³.

The semirigid shell 4 can be produced by molding or coldinjection-molding of polymeric materials such as nylon or polypropylene.Preferably, the surface of the shell in contact with the layer of foamedresin is oxidized by combustion, forming on its surface radicals thatcan chemically attach to the foamed resin of the filler.

The method for manufacturing integral saddles with gel insert of thetype shown in FIGS. 1 and 2 is schematically shown in FIGS. 6 to 15, andentails the use of a mold 10 illustrated in FIG. 3.

The mold 10 is formed by a lower part 11, by an upper part 12, by anintermediate locking plate 13, and preferably by a second undercut plate14. The lower part 11 can be obtained for example from an aluminum alloyblock, on the upper surface of which a cavity 15 is formed; this cavityis open upward and is shaped complementarily to the resting surface ofthe support which coincides with the outer surface of the covering 2.Holes 16 are present on the bottom of the cavity 15 and are connected,by means of channels 17, to a manifold channel 18 which can in turn beconnected, by means of a pipe, to a vacuum pump V or to an externalcompressor P. The lower part 11 also includes a coil 19 through which aliquid at a temperature between 50° and 80° C. flows in order to keepthe lower part of the mold at a temperature of approximately 40° C.throughout the process. The lower part 11 is anchored to a support 20which carries a bracket 21.

The upper part 12 of the mold can also be obtained from an aluminumplate and is preferably internally provided with a heating coil 22. Itslower face 23 is shaped complementarily to the cavity 15 and to theouter face of the semirigid shell 4 to allow its detachable couplingsimply by pressing. The end of the part 12 is hinged at 24 to thebracket 21 so as to rotate upward and expose the cavity 15.

The locking plate 13 has a flat lower face 25 that lies peripherallywith respect to the cavity 15 with an inner edge that coincidesapproximately with the upper margin of the cavity 15 and is also pivotedto the bracket 21 at 24.

The plate 14 has an upper face 26 that is similar to the face 25 of theplate 13 but has, with respect to the face 25, an internal border thatprotrudes inward by a few millimeters to form an undercut with respectto the cavity 15. In order to improve the seal between the plate 14 andthe lower part 11 of the mold, a peripheral slot, in which an annulargasket 27 made of elastomeric material is inserted, can be formed on themold.

The method for manufacturing the support 1 according to the inventionincludes a first step, shown in FIG. 6, that consists in opening themold by lifting the upper part 12 and the plate 13 with respect to thelower part 11, either manually or by means of mechanical actuators,allowing the undercut plate 14 to rest on the part 11.

The second step entails the laying of a covering sheet 2 on the plate 14so as to fully cover the cavity 15, with borders that protrude beyondthe edge of the plate 14. Immediately after this, the sheet 2 is heatedfor a few seconds with an UV (ultraviolet) lamp 28 or with a stream ofhot air or with infrared rays, so as to raise it to a temperaturebetween 40° and 150° C., preferably between 80° and 100° C., which isclose to the plasticization temperature of the base material.

In the subsequent step, shown in FIG. 8, the locking plate 13 is loweredonto the sheet 2, securing its border against the undercut plate 13.Immediately after this, the sheet is preformed by means of a presser 29so as to stretch it and move it toward the bottom of the cavity 15.

The step shown in FIG. 8 entails the forming of a vacuum on the surfaceof the cavity 15 so as to make the covering 2 adhere perfectly anddeform permanently. Conveniently, a depression 30 is formed on thebottom of the cavity 15 of the mold and is suitable to accommodate apart of the filler 3, forming a corresponding protrusion that extendsfrom the upper surface of the support.

During mechanical and vacuum forming, the border of the sheet 2 isretained along the entire perimeter of the saddle in different mannersbetween the facing surfaces 25 and 26 of the plates 13 and 14respectively. This is done to firmly secure the border of the covering 2in the maximum stress regions, allowing instead a limited slip of thematerial in the remaining regions of the border, in order to avoid theforming of creases and surface discontinuities. For this purpose, thefaces 25 and 26 of the plates 13 and 14 are kept so that they face oneanother along the contour of the cavity 15 with a play Δ which is equalto the thickness of the covering plus 0.1÷0.15 mm. In the regions ofmaximum stress of the coating, such as the saddle tip and the lateralprotrusions, there are additional retention means which are suitable toincrease the retaining action by virtue of a larger surface for grippingthe material of the covering. As shown in FIGS. 4 and 5, these retentionmeans can be constituted by rounded protrusions 31 that are formed onone of the surfaces 25 and 26, for example on the surface 25, and arearranged opposite to complementarily shaped recesses 32 formed on theopposite face 26. In the specific case, the protrusions 31 and therecesses 32 are located toward the tip and the lateral protrusions ofthe saddle, where the tighter curvature radii of the outer profileproduce the highest stresses during forming.

The step of forming the covering 2 is followed by a step in which thegel compound is poured onto the bottom of the deformed sheet by means ofa first foaming head A, as shown in FIG. 11. Conveniently, the foaminghead A deposits the mixed and fluid gel compound at a temperature ofapproximately 30° C. The pre-polymerized mixture is poured in presetproportions and quantities at the depression 30 of the bottom of thecavity 15 so as to fill it completely. This is followed by a step ofinitial polymerization of the compound at a constant temperature whichis maintained by the coil 19 inserted in the lower part 11 of the mold.According to the invention, the partial polymerization time Tp must beset so as to allow the gel compound to assume a certain consistency andshape of its own, such that it is not deformed by the subsequent pouringof a second filler layer made of a different material. In particular,the fluid gel compound forms a flat, meniscus that forms the separationsurface of the compound with respect to an adjacent filler layer.

However, polymerization is only partial, so as to prevent the closing ofall the chains of the polymeric compounds of the composition, leaving onthe surface of the meniscus several open chains and free radical groupsthat can bind with the expandable resin that will subsequently bepoured.

During the partial polymerization of the gel compound, a shell 4, meantto be integrated in the support as shown in FIG. 11, is coupled to theupper part 12 of the mold.

After the partial polymerization time Tp (of 30 to 80 seconds andpreferably 50 to 60 seconds) has elapsed, the expandable polyurethaneresin is deposited by means of a second foaming head B which is similarto the first one, as shown in FIG. 12.

The mold is then fully closed and sealed, except for some lateral vents,by placing the upper part 12 over the lower part 11 and locking theintermediate plates 13 and 14 against the latter, as shown in FIG. 14.The mold is kept in this condition for a time Tc until the polyurethaneresin has fully foamed and cross-linked. At the same time, chemicalbonds form between the gel compound and the polyurethane foam at theseparation surface of the two materials which coincides with themeniscus of gel compound, and between the gel compound, the polyurethaneresin, and the covering 2. In this manner the insert 7 of gel compoundis firmly anchored to the layer of foamed polyurethane 6 and the twomaterials are in turn anchored to the covering 2. The entire assembly isfirmly anchored to the shell 4, forming an integral support which ispractically finished except for the excess border of the covering sheet2.

During the full polymerization step the entire mold may be rockedslightly about a substantially horizontal axis 33 to tilt the cavity 15and facilitate discharge of the gases produced inside the mold by thefoaming of the resin, by the exothermic addition-polymerizationreactions and by the polymerization of the various components.

FIG. 15 illustrates the final step of opening of the mold by lifting theupper part 12, the locking plate 13 and the undercut plate 14 to allowextraction of the finished saddle. In order to facilitate expulsion ofthe support 1, the stream of air in the manifold may be reversed byconnecting it to a compressor P and producing a slight overpressuresufficient to separate the support from the bottom of the cavity 15.

In order to completely finish the support it is sufficient to remove theexcess material of the covering sheet by means of a continuous cutter.

FIG. 16 is a top view of an apparatus that uses a series of molds of thetype shown in FIG. 3 and uses the above described method in asemi-continuous manner. The apparatus includes a turntable 34 that isdivided into a certain number of sectors 35 that form the bases for thesupports 20 of the molds 10. The turntable is rotated by means of agearmotor 36 in steps which have an angular extent equal to that of thesectors in order to place the molds in front of respective stations. TheUV-ray lamp 28 and the foaming heads A and B are arranged along theperimeter of the turntable 34; the heads can move radially to placethemselves on the depression 30 of the cavity 15. The covering sheet 2and the shell 4 are inserted manually or by means of mechanicalmanipulators. Time various stations are angularly spaced so as toproduce the sequence shown FIGS. 6 to 15.

With respect to this sequence it is possible to add a step in which anon-stick releasing product is sprayed along the border of the surface23 of the upper part 12 of the mold to prevent the polyurethane foamfrom sticking to the mold. This step, added after the mold opening stepshown in FIG. 6, can be produced by means of an appropriate automaticspray head 37. Actuation of the various parts and rotation of theturntable are controlled by a PLC-type control unit possibly connectedto a PC capable of displaying the main parameters of the process.

Although the method and the support according to the invention have beendescribed in a preferred embodiment, it is evident that they aresusceptible to numerous modifications and variations, all of which arewithin the scope of the inventive concept expressed in the accompanyingclaims. For example, the manufacturing apparatus illustrated in FIG. 16can use a closed-loop conveyor belt instead of a turntable withoutabandoning the scope of the invention.

I claim:
 1. An integral elastic support, comprising an upper coveringmade of flexible laminar material superimposed on a filler thatcomprises a layer of foamed resin anchored to a shell made ofsubstantially rigid plastic material, wherein said filler is chemicallybonded both to said covering and to said shell to form an integralsupport, at least one insert or layer of a gel compound being interposedbetween said covering and said foamed resin filler to form with saidlatter a surface of separation, said gel compound being chemicallybonded by an addition-polymerization reaction both to said foamed resinlayer and to said covering, said insert being located in regions ofmaximum pressure for the body of the user wherein said gel insert isself-supporting and said surface of separation is substantially flat. 2.Support according to claim 1, wherein said insert made of gel compoundis placed directly in contact with said covering with the interpositionof a thin layer of polyurethane primer anchored to the base material ofthe covering and is chemically bonded both to the covering and to saidfoamed resin layer.
 3. Support according to claim 1, wherein said insertmade of gel compound is placed directly in contact with said coveringwith the interposition of a thin layer of polyurethane primer anchoredto the base material of the covering and is chemically bonded both tothe covering and to said foamed resin layer, said gel compound being amixture of a polyurethane matrix with a liquid dispersant that has noplasticizers and has characteristics of high consistency, stability andlack of migration of its components.
 4. An integral elastic supportcomprising:a rigid plastic shell; a filler layer of foamed resinanchored to the shell; a flexible upper covering secured to the shellenclosing the filler layer, said filler being chemically bonded to bothsaid covering and to said shell forming an integral structure; and atleast one insert layer of a gel compound being interposed between saidcovering and said foamed resin filler to form with said latter a surfaceof separation, said gel compound being chemically bonded by anaddition-polymerization reaction both to said foamed resin layer and tosaid covering, said insert layer being located in regions of maximumpressure for the body of the user wherein said gel insert isself-supporting and said surface of separation is substantially flat. 5.The support according to claim 4, wherein said covering comprises alaminate including a base layer and said insert layer is located incontact with said covering.
 6. The support according to claim 5 furtherincluding a relatively thin layer of polyurethane primer adhered to thebase material of the covering and chemically bonded both to the coveringand to said filler layer of foamed resin.
 7. The support according toclaim 4 further including a relatively thin layer of polyurethane primeranchored in direct contact to the covering and chemically bonded both tothe covering and to said filler layer of foamed resin.
 8. The supportaccording to claim 4 wherein said gel compound comprises a mixture of apolyurethane matrix with a liquid dispersant.
 9. The support accordingto claim 7 wherein the gel compound comprises a mixture of about 20% byweight of a polyurethane matrix with high relative molecular weight atabout 80% by weight of a liquid dispersant.
 10. The support according toclaim 9 wherein the liquid dispersant comprises a polyhydric alcohol.11. The support according to claim 9 wherein the matrix is formedwithout plasticizers.
 12. The support according to claim 9 wherein thegel compound exhibits a relatively high level of consistency andstability and a relatively low level of migration.
 13. An integralelastic support comprising:a substantially rigid plastic shell; a fillerlayer of foamed resin anchored to the shell; a flexible upper coveringsecured to the shell enclosing the filler layer, said filler beingchemically bonded to both said covering and to said shell forming anintegral structure; at least one insert layer of gel compound beinginterposed between said covering and said foamed resin filler to formwith said latter a surface of separation, said insert layer beinglocated in regions of maximum pressure for the body of the user; meansfor constraining said gel layer against lateral movement with respect tosaid foamed resin filler; wherein said gel insert is self-supporting andsaid surface of separation is substantially flat; and wherein means forsaid constraining comprises chemical bonds between the gel layer andsaid foamed resin filler along said surface of separation.